No abstract

The cotton boll weevil, Anthonomus grandis (Coleoptera: Curculionidae), is the major insect pest of cotton in the Americas. Although the demographic and dispersion patterns of the cotton boll weevil in the USA and Mexico were well characterized, in Brazil the information is scarce and does not include the main cotton‐producing regions of the country. Thus, our objective was to apply a phylogeographic approach sequencing a gene fragment of the cytochrome c oxidase subunit I (COI) to estimate the genetic diversity, identify the genetic strains, and describe the dispersion routes of the cotton boll weevil in the Brazilian territory. The COI marker revealed a low genetic diversity of the cotton boll weevil with only two haplotypes in Brazil. The haplotypes are genetically related to individuals from the eastern region of the USA and Mexico, which suggests a recent invasion event in Brazil. The genetic structure of COI haplotypes indicates a low dispersion of boll weevils between north/northeast and midwest/southeast regions of Brazil. The genetic drift and low gene flow during the insect expansion explain the COI haplotype distribution. The genetic structure of the cotton boll weevil in Brazil is novel information and provides valuable insight for the design of suitable pest management practices against this key pest species in the country.

Spodoptera frugiperda is a serious pest of maize and other crops worldwide. The integration of control tactics is recommended for S. frugiperda suppression because reports of insecticide and Bt plant-resistance are frequent. Biological control agents would be an alternative to improve S. frugiperda control in agricultural areas. We constructed a species-specific molecular marker to detect S. frugiperda DNA in predators' gut content and estimated the predation rates of ladybugs and earwigs on S. frugiperda in maize crops. Predators were sampled in Pirassununga, São Paulo state, Brazil, in 2020 and 2021. Using the species-specific molecular marker in laboratory conditions, we estimated the half-life time to detect S. frugiperda DNA in the gut contents of Hippodamia convergens as 6.16 h and Doru luteipes as 25.72 h. The weekly predation rate of S. frugiperda by predators in maize crop varied from 0 to 42.1% by ladybugs and from 0 to 9.2% by D. luteipes. Predation events on S. frugiperda by predators were more frequent during the maize reproductive stage. Our results confirmed that predators might contribute to S. frugiperda suppression in maize fields. However, further studies of prey-predator interactions and agricultural landscapes are essential for a better understanding of predator dynamics in crops.

Spodoptera frugiperda is a serious pest of maize and other crops worldwide. The integration of control tactics is recommended for S. frugiperda suppression because reports of insecticide and Btplant-resistance are frequent. Biological control agents would be an alternative to improve S. frugiperda control in agricultural areas. We constructed a species-specific molecular marker to detect S. frugiperda DNA in predators’ gut content and estimated the predation rates of ladybugs and earwigs on S. frugiperda in maize crops. Predators were sampled in Pirassununga, São Paulo state, Brazil, in 2020 and 2021. Using the species-specific molecular marker in laboratory conditions, we estimated the half-life time to detect S. frugiperda DNA in the gut contents of Hippodamia convergens as 6.16 h and Doru luteipes as 25.72 h. The weekly predation rate of S. frugiperda by predators in maize crop varied from 0 to 42.1% by ladybugs and from 0 to 9.2% by D. luteipes. Predation events on S. frugiperda by predators were more frequent during the maize reproductive stage. Our results confirmed that predators might contribute to S. frugiperda suppression in maize fields. However, further studies of prey–predator interactions and agricultural landscapes are essential for a better understanding of predator dynamics in crops.